The Stuttgart midfielder, who endured relegation from the Bundesliga this season, was omitted from Anghel Iordanescu's group to take to France, which was announced by the Romania Football Federation on Tuesday.
Adrian Ropotan and Ioan Hora of Pandurii Targu Jiu, Steaua Bucharest's Alin Tosca, and Universitatea Craiova teenager Andrei Ivan also missed out.
Head coach Iordanescu confirmed he will invite all five players to France as guests of the team after their disappointment.
"I thank all the players who took part in the training session in Italy, and the clubs where they have developed. I'm so sorry to have to give up five players," he said in a statement released by the FRF's website.
"Together, with the leadership of the Romanian Football Federation, we decided that these five players will be our guests in France during the European Championship."
Romania face Georgia in a friendly on Friday before they begin their Euro 2016 campaign against host nation France on June 10. They also face Switzerland and Albania in Group A.
Romania squad in full:
Goalkeepers: Ciprian Tatarusanu (Fiorentina), Costel Pantilimon (Watford), Silviu Lung Jr (Astra)
Defenders: Cristian Sapunaru (Pandurii Tg. Jiu), Alexandru Matel (Dinamo Zagreb), Vlad Chiriches (Napoli), Valerica Gaman (Astra Giurgiu), Dragos Grigore (Al Sailiya), Cosmin Moti (Ludogorets), Razvan Rat (Rayo Vallecano), Steliano Filip (Dinamo)
Midfielders: Mihai Pintilii (Steaua Bucharest), Ovidiu Hoban (Hapoel Be'er Sheva), Andrei Prepelita (Ludogorets), Adrian Popa (Steaua Bucharest), Gabriel Torje (Osmanlispor), Alexandru Chipciu (Steaua Bucharest), Nicolae Stanciu (Steaua Bucharest), Lucian Sanmartean (Al Ittihad)
Forwards: Claudiu Keseru (Ludogorets), Bogdan Stancu (Genclerbirligi), Florin Andone (Cordoba), Denis Alibec (Astra).